OLD THREAD DAC End by Andrea Ciuffoli

[Salas]

Iset=33R, old used part in the bin box.

Leave it there then, not that critical a position, and hey, has golden legs. Gold is back.

 

[housing]

Leave it there then, not that critical a position, and hey, has golden legs. Gold is back.

Yes, that's an RMG, not RMA.

 

[flocchini]

Very nice build.

Where did you secure the HV shunt board?

Did you try the Quanghao's HV board? (Sorry if I missed this)

Thanks

Bob

 

[Salas]

Yes, that's an RMG, not RMA.

Good thing is that the production HV board works OK then? No problems? You must be the first fully testing it and presenting a photo here, yes?

 

[housing]

Very nice build.

Where did you secure the HV shunt board?

Did you try the Quanghao's HV board? (Sorry if I missed this)

Thanks

Bob

Hi Bob,

I didn't order quanghao's original HV board but ordered his Salas shunt HV board right from the beginning.

Thanks,

housing

 

[housing]

Good thing is that the production HV board works OK then? No problems? You must be the first fully testing it and presenting a photo here, yes?

I think it's perfect. I will hook it up to an oscilloscope soon.

 

[Nikon1975]

Salas,

I still do not manage to bring the voltages more than 5.2 V for the positive and 5.1 V for the negatives. I think that my leds have a ref voltages too high. Could it be ? Which one can I try to replace to make a test ?

Thanks,

Davide

 

[Salas]

This sounds like a low voltage reg question I suppose. Check output Mosfet's VGS at you max. If its not circa 4V, then your current is robbed by the TL431s and you need even lower Rset as I have learned reading this thread. If it is alone it works anyway. What value of resistor you got as Rset now?

 

[housing]

Salas,

I still do not manage to bring the voltages more than 5.2 V for the positive and 5.1 V for the negatives. I think that my leds have a ref voltages too high. Could it be ? Which one can I try to replace to make a test ?

Thanks,

Davide

My measurements may be of help to you:

All LED's sag about 1.91volt - 1.92 volt each
All 2SK170BL's Idss = about 6.5mA
AC voltage in = 10 volt by multimeter

Use 24R 1W for +ve and -ve rail of analogue supply, voltage easily adjusted to 5.6 volt and doesn't sag with load.
Positive rail voltage across 24R=2.104 volt, CCS is about 87.7 mA
Negative rail voltage across 24R=2.056 volt, CCS is about 85.7 mA. So I add a 1K in parallel with the 24R to make the CCS more like 87.7 mA

Use 2x24R in parallel for the +5V digital supply, voltage easily adjusted to 5.6 volt without load (at 166.6 mA output already) but sags to 5.32 volts with load.
Voltage across 12R = 1.999 volts, CCS is about 166.6 mA

All voltage measurement after TL431 for the IC's consumption are fine and about 5 Volt.

 

[Salas]

The +5V alone branch can be challenged for even more CCS setting I have gathered. What is its output Mosfet's VGS when feeding the DAC?

 

[housing]

The +5V alone branch can be challenged for even more CCS setting I have gathered. What is its output Mosfet's VGS when feeding the DAC?

I didn't measure it. I'll do it some time later and report.

 

[fredlock]

Hi Fredlock,

Not yet. But the DAC, LV and HV shunt supply portions have been checked working in order.

This is the picture of my project completed so far. Just bought a chassis and it just fits.

Goob Job Housing! That's looking great. Where did you buy your chasis? and how much did it cost you? What tubes are you planning to use?

 

[housing]

Goob Job Housing! That's looking great. Where did you buy your chasis? and how much did it cost you? What tubes are you planning to use?

I got it from a local diy shop selling only boutique parts. It costs me about USD71, all aluminium, with ventilating slots throughout the top cover.

I'll be using a pair of 5687, Jan Sylvania, said to be matched from a US dealer on eBay.

 

[klaju1955]

1. pathetic (1 set)
2. cchean ( 2 sets )
3. Lucylu (1 set)
4. Ulyses31 (1 set)
5. damohpi (1 set)
6. mikvous (3 sets)
7. gipione ( 1 set)
8. flocchini (1 6h6P if done, 1 Salas HV)
9. belkoff (full set dac end 2 + 1 6h6P if done, 1 Salas HV) + schematic for each PCB

10. klaju1955 (1 set)

 

[Nikon1975]

I did some measurements:

Regulator #1:
Rset = 8.2 ohm
Vgs = 4 V
Vout = 5.241

Regulator #2:
Rset = 27 ohm
Vgs = 3.8 V
Vout = 5.232 V

Regulator #3(Negative):
Rset = 27 ohm
Vgs = 3.4 V
Vout = 5.11 V

I do not have any drop with load attached.

I have average 1.85 V drop across the leds.

If this is fine, I am happy. The unit works perfectly, it is dead silent. (With not music )

Best Regards,

Davide

 

[Salas]

Looks normal to me.

 

[Nikon1975]

That's what I love to hear

D.

 

[Nikon1975]

I am doing some experiment with the CCS and led. I did not listen to it yet.

Some pictures.

I use a DN2450 with a 1.5 K set resistor, to set current to 15 mA per channel.

I have 3.4 V on the cathodes (matched). It should not really matter with the CCS. Is it correct ?

D.

 

[regal]

I am doing some experiment with the CCS and led. I did not listen to it yet.

Some pictures.

I use a DN2450 with a 1.5 K set resistor, to set current to 15 mA per channel.

I have 3.4 V on the cathodes (matched). It should not really matter with the CCS. Is it correct ?

D.

With a CCS it becomes more critical for tubes to be matched. You may want to play 1khz test tones at 0dbs and measure the output with your dmm to ensure both channels put out the same voltage. Thats the only thing I would worry about.

 

[fredlock]

I did some measurements:

Regulator #1:
Rset = 8.2 ohm
Vgs = 4 V
Vout = 5.241

Regulator #2:
Rset = 27 ohm
Vgs = 3.8 V
Vout = 5.232 V

Regulator #3(Negative):
Rset = 27 ohm
Vgs = 3.4 V
Vout = 5.11 V

I do not have any drop with load attached.

I have average 1.85 V drop across the leds.

If this is fine, I am happy. The unit works perfectly, it is dead silent. (With not music )

Best Regards,

Davide

Hi Davide,

I know that there's a lot of TL431 on Mouser's list but can you let me know what TL431 did you use? Is it a Texas instrument or On Semi? Do you have a part number.

I think the TL431 are the one causing this issues for the shunt regulator to function properly. The reason I ask is because, you have the most successful shunt reg working properly, even with the load connected.